XIAP inhibitor 1396-12 induces apoptosis independent of Bcl-2, Bcl-X_L, and caspase 8. Jurkat cells lacking caspase 8 (I2.1)³²  (A,▵), Jurkat cells overexpressing Bcl-2³¹  (B,▵), U937 cells overexpressing Bcl-xL (C, ▵), or the corresponding vector controls (6 × 10⁵/mL; □) were treated with increasing concentrations of the XIAP inhibitor 1396-12. As controls, Jurkat cells lacking caspase 8 (D, ▵) were treated with increasing concentrations of CH-11 anti-Fas antibody (100 ng/mL). Also, Jurkat cells (E) and U937 cells (F) overexpressing Bcl-2 or Bcl-xL (▵), respectively, were treated with increasing concentrations of Ara-C. Apoptosis was measured by annexin V staining. The mean plus or minus SD of 3 independent experiments is shown.